Surface acoustic wave sensor
A surface acoustic wave (SAW) sensor includes a surface acoustic wave material and a comb-teeth electrode. The surface acoustic wave material is to be arranged at a place where the surface acoustic wave material is distorted by physical quantity such as stress. The comb-teeth electrode is arranged on the surface of the surface acoustic wave material to excite a surface acoustic wave to the surface acoustic wave material. The surface acoustic wave material has a sapphire board and a ScAlN film arranged on a surface of the sapphire board.
1. A surface acoustic wave sensor comprising:
a surface acoustic wave material to be arranged at a place where the surface acoustic wave material is distorted by physical quantity; and
a comb-teeth electrode arranged on the surface acoustic wave material to excite a surface acoustic wave to the surface acoustic wave material, wherein
the surface acoustic wave material has a sapphire board and a ScAlN film arranged on a surface of the sapphire board, and
the surface acoustic wave material is arranged at the place where a stress in a propagation direction of the surface acoustic wave and a stress in a perpendicular direction perpendicular to the propagation direction are applied to the surface acoustic wave material.
2. The surface acoustic wave sensor according to claim 1 , wherein
a Sezawa wave is used as the surface acoustic wave.
3. The surface acoustic wave sensor according to claim 1 , wherein
the comb-teeth electrode has
a Sezawa wave comb-teeth electrode that excites a Sezawa wave, and
a Rayleigh wave comb-teeth electrode that excites a Rayleigh wave,
the Sezawa wave comb-teeth electrode corresponds to a first element that detects physical quantity, and
the Rayleigh wave comb-teeth electrode corresponds to a second element for temperature compensating.
4. The surface acoustic wave sensor according to claim 3 , wherein
the Sezawa wave comb-teeth electrode has a plurality of comb-teeth parts with a first pitch,
the Rayleigh wave comb-teeth electrode has a plurality of comb-teeth parts with a second pitch, and
the first pitch and the second pitch are different from each other, and are set such that a frequency of a drive signal for driving the Sezawa wave comb-teeth electrode and a frequency of a drive signal for driving the Rayleigh wave comb-teeth electrode are the same.
5. The surface acoustic wave sensor according to claim 3 , further comprising:
a Sezawa wave correspondence electrode disposed on the surface acoustic wave material to correspond to the Sezawa wave comb-teeth electrode, the Sezawa wave correspondence electrode receiving or reflecting a Sezawa wave excited by the Sezawa wave comb-teeth electrode;
a Sezawa wave propagation path where a Sezawa wave spreads between the Sezawa wave comb-teeth electrode and the Sezawa wave correspondence electrode on the surface acoustic wave material;
a Rayleigh wave correspondence electrode disposed on the surface acoustic wave material to correspond to the Rayleigh wave comb-teeth electrode, the Rayleigh wave correspondence electrode receiving or reflecting a Rayleigh wave excited by the Rayleigh wave comb-teeth electrode; and
a Rayleigh wave propagation path where a Rayleigh wave spreads between the Rayleigh wave comb-teeth electrode and the Rayleigh wave correspondence electrode on the surface acoustic wave material, wherein
a part of the Sezawa wave propagation path and a part of the Rayleigh wave propagation path overlap with each other.
6. The surface acoustic wave sensor according to claim 1 , wherein
a substrate surface of the sapphire board has a plane direction of C-plane, and
the propagation direction is inside of A-plane or in a direction defined by rotating by 60 degrees relative to the A plane.
7. A surface acoustic wave sensor comprising:
a surface acoustic wave material to be arranged at a place where the surface acoustic wave material is distorted by a physical quantity; and
a comb-teeth electrode arranged on the surface acoustic wave material to excite a surface acoustic wave to the surface acoustic wave material, wherein
the surface acoustic wave material has a sapphire board and a ScAlN film arranged on a surface of the sapphire board,
the comb-teeth electrode has
a Sezawa wave comb-teeth electrode that excites a Sezawa wave, and
a Rayleigh wave comb-teeth electrode that excites a Rayleigh wave,
the Sezawa wave comb-teeth electrode corresponds to a first element that detects physical quantity, and
the Rayleigh wave comb-teeth electrode corresponds to a second element for temperature compensating.
8. The surface acoustic wave sensor according to claim 7 , wherein
the Sezawa wave comb-teeth electrode has a plurality of comb-teeth parts with a first pitch,
the Rayleigh wave comb-teeth electrode has a plurality of comb-teeth parts with a second pitch, and
the first pitch and the second pitch are different from each other and are set such that a frequency of a drive signal for driving the Sezawa wave comb-teeth electrode and a frequency of a drive signal for driving the Rayleigh wave comb-teeth electrode are the same.
9. The surface acoustic wave sensor according to claim 7 , further comprising:
a Sezawa wave correspondence electrode disposed on the surface acoustic wave material to correspond to the Sezawa wave comb-teeth electrode, the Sezawa wave correspondence electrode receiving or reflecting a Sezawa wave excited by the Sezawa wave comb-teeth electrode;
a Sezawa wave propagation path where a Sezawa wave spreads between the Sezawa wave comb-teeth electrode and the Sezawa wave correspondence electrode on the surface acoustic wave material;
a Rayleigh wave correspondence electrode disposed on the surface acoustic wave material to correspond to the Rayleigh wave comb-teeth electrode, the Rayleigh wave correspondence electrode receiving or reflecting a Rayleigh wave excited by the Rayleigh wave comb-teeth electrode; and
a Rayleigh wave propagation path where a Rayleigh wave spreads between the Rayleigh wave comb-teeth electrode and the Rayleigh wave correspondence electrode on the surface acoustic wave material, wherein
a part of the Sezawa wave propagation path and a part of the Rayleigh wave propagation path overlap with each other.
10. The surface acoustic wave sensor according to claim 7 , wherein
a substrate surface of the sapphire board has a plane direction of C-plane, and
the propagation direction is inside of A-plane or in a direction defined by rotating by 60 degrees relative to the A-plane.
11. The surface acoustic wave sensor according to claim 7 , wherein the surface acoustic wave material is arranged at the place where a stress in a propagation direction of the surface acoustic wave and a stress in a perpendicular direction perpendicular to the propagation direction are applied to the surface acoustic wave material.